The Genesis Mission: Solar Wind Conditions and the Application of ACE/SWICS in Situ Measurements to the Genesis Sample Analysis

The Genesis samples must be placed in the context of the solar and solar wind conditions under which they were collected. Solar wind is fractionated from the photosphere by the forces that accelerate the ions off of the Sun. This fractionation appears to be ordered by the first ionization potential (FIP) of the elements, with the tendency for low-FIP elements to be over-abundant in the solar wind relative to the photosphere, and high-FIP elements to be under-abundant (e.g. Geiss, 1982; von Steiger et al., 2000). In addition, the extent of elemental fractionation differs across different solar-wind regimes. Therefore, Genesis collected solar wind samples sorted into three regimes: `fast wind' or `coronal hole' (CH), `slow wind' or `interstream' (IS), and `coronal mass ejection' (CME), in addition to a set of collectors that were continuously exposed to the solar wind. Here we report on the bulk and regime-specific solar wind conditions from in-situ instruments over the course of the collection period. Our analysis of Genesis samples has been complemented by composition data from the SWICS (Solar Wind Ion Composition Spectrometer) instrument on ACE (Gloekler et al., 1998). Both spacecraft were operational at the same times, and were both in halo orbits about the L1 point. Thus it is straightforward to co-register solar wind measurements from each. We have used the ACE data to 1) make comparisons between in situ composition measurements and preliminary elemental abundances determined from the Genesis samples, including Ne, Mg, and He; 2) determine the expected deposition profiles of various solar wind elements in the Genesis sample material; 3) determine the fractional contribution of different oxygen charge states to the oxygen isotope sample on the Genesis concentrator targets, and 4) to examine the FIP fractionation between solar wind regimes. Ultimately this latter analysis will be compared to the Genesis regime-specific samples to further investigate FIP fractionation.